The basic determination which a gynecologist must make afresh with each new patient is whether a pregnancy has a favorable prognosis for vaginal delivery, or whether cesarean delivery will probably be required, as is the case for patients having contracted pelves.
The adult pelvis is composed of four bones defining an opening through which the normal delivery of a fetus takes place. If the passageway is not of adequate dimensions, delivery by cesarean section is indicated. One of the most significant dimensions in this connection is the distance between the ischial spines. Heretofore this distance has been determined by palpating the patient, or with the aid of X-ray pelvimetry. The former process relies heavily on the skill of the physician, and the latter requires the use of equipment and personnel not always available, and has the danger of radiological damage to the mother or fetus, in addition to its high cost.